1. Field of the Invention
The present invention relates to a dendritic molecule containing metal phthalocyanine and an organic light emitting diode comprising the same, and more particularly, to a dendritic molecule that can be used to form a hole injection layer and an electron injection layer by a solution process that uses an organic solvent, and can improve luminance and emitting efficiency of an organic light emitting diode and an organic light emitting diode including the same.
2. Description of the Related Art
Organic light emitting diodes are self-emissive displays using a phenomenon that when voltage is applied to a fluorescent or phosphorous organic film, electrons and holes are combined in the organic film for light to be emitted. Since organic light emitting diodes are small-sized, have simplified components and simple manufacturing processes, can implement high image quality and high color purity, have low power consumption, can perfectly implement live images and the like, extensive research on organic light emitting diodes has been actively conducted.
Organic light emitting diodes can include several layers such as hole-related layers, for example, a hole injection layer and a hole transport layer and electron-related layers, for example, an electron transport layer and an electron injection layer, in addition to an organic emissive layer, between an anode or a cathode. The hole-related layers and the electron-related layers adjust injection or mobility of electrons or holes from the cathode and the anode. In addition, the anode may comprise an inorganic material such as ITO or IZO, and thus may have a high surface hardness. Surface toughness of the anode may be reduced by introducing a hole injection layer to the organic light emitting diode before a hole transport layer or an emissive layer is formed. In some cases, by introducing a functional group that can improve chemical binding with or absorption to an anode into a material used to form a hole injection layer, adhesion at an interface between an anode (inorganic) and an organic layer (organic) can be improved. In addition, when a difference in ionization potential between the work function of the anode comprising ITO and IZO and an organic layer such as a hole transport layer or an emissive layer that is formed on the anode is so large that hole injection is difficult, a hole injection layer can be introduced in order to easily inject holes. The hole injection layer that is formed on the anode can be also referred to as a buffer layer.
Materials that can form the hole injection layer by a solution process are preferable since the solution process costs low. Of these materials, a polymer material such as PEDOT/PSS in which poly(ethylenedioxy)thiophene (PEDOT) is doped with polystyrene sulfonate (PSS) is commercially available. The material (PEDOT/PSS) is commercially available as a product name of Baytron-P from Bayer AG, and widely used as a material used to form a hole injection layer. A deposition process of a hole injection layer uses an aqueous solution, thereby not being able to be performed within a glove box. Therefore, after the hole injection layer is formed on an electrode outside the glove box, a heat-treatment process, in the glove box, that uses a hot plate or a vacuum oven is required for removing moisture remaining. In addition, a subsequent organic layer is also formed inside the glove box in order to prevent the infiltration of moisture and oxygen.
PSS in PEDOT/PSS is degraded by a reaction with electrons to produce a material such as sulfate or the like. As a result, the material is diffused into an adjacent organic film, for example, an emissive layer. However, the diffusion of the material from a hole injection layer into the emissive layer causes exciton quenching, resulting in reduction in efficiency and lifetime of an organic light emitting diode.
To address such problems, there is a need to develop a material that can be used to form a hole injection layer by a solution process that uses an organic solvent, and has good adhesion to ITO and IZO.